The present invention relates to a metal interconnect structure, and particularly to a metal interconnect structure including a copper-containing structure having a selectively deposited and self-aligned copper encapsulation layer thereupon and methods of manufacturing the same.
Metal interconnect structures employed in semiconductor chips employ copper-containing structures for copper-containing structures and metal vias, which include copper as a predominant composition. Exposed surfaces of such copper-containing structures tend to be oxidized in air after a planarization process such as chemical mechanical planarization (CMP). Presence of a copper oxide layer on surfaces of copper-containing structures degrades adhesion of the copper-containing structures to a dielectric cap layer deposited thereupon, thereby adversely impacting the reliability of the metal interconnect structure during operation.
Benzotriazole (BTA) can be applied to exposed copper surfaces after chemical mechanical planarization to reduce oxidation of copper. However, BTA also causes “hollow metal” problems by causing formation of microcavities on the surface of copper-containing structures, thereby aggravating the reliability of the metal interconnect structure during operation.
The reliability of a metal interconnect structure is closely related to adhesion of surfaces of a copper-containing structure to a dielectric material layer formed thereupon. The greater the adhesive strength between copper atoms in a copper-containing structure and a dielectric material formed as a cap thereupon, the greater the resistivity to electromigration of the material in the copper-containing structure when electrical current flows therethrough during the usage of a semiconductor chip containing the copper-containing structure.